Yarn heater



Sept. 30, 1969 N. J. STODDARD ET AL YARN HEATER Fild Aug. 8. 1967 2Sheets-Sheet l mvsu roras, Mam/1s J sraamza Fa in/V. Swap/W0 Sept. 30,1969 J, STODDARD ET AL 3,469,384

YARN HEATER Filed Aug. 8, 1967 2 Sheets-$heet 2 //V VE/VTOZSI Mae/004s J57000/2/20 fo s/e714! 570004/20 United States Patent 3,469,384 YARNHEATER Nicholas J. Stoddard and Robert W. Stoddard, Berwyn, Pa.,assignors to Leesona Corporation, Warwick, R.I., a corporation ofMassachusetts Filed Aug. 8, 1967, Ser. No. 659,181 Int. Cl. Dtllh 13/26;D02g 3/02 US. CI. 57-34 43 Claims ABSTRACT OF THE DISCLOSURE BACKGROUNDOF THE INVENTION This invention relates to yarn heaters of the typeemployed to impart a controlled quantity of heat to strand materials,such as temperature sensitive textile yarns being passed therethrough.In one aspect, the invention relates to yarn heaters for use inconjunction with equipment whereby thermoplastic yarn is textured by afalse twsiting operation. The invention also deals with a method ofheating twisted yarn.

Techniques for continuously texturing or bulking thermoplastic textileyarn by false twisting are being used with great success. Asimprovements in various aspects of these techniques make possible theprocessing of yarn at higher and higher linear speeds, the need toimpart heat to the yarn at sufficiently high rates becomes increasinglymore critical. Thus one finds that in thermal yarn processing equipmentof a given type wherein yarn contact heaters of relatively short lengthwere employed in order to process yarn at given lineal speeds, asimprovements are made which permit the processing of yarns at higherlineal s eeds therein it becomes necessary to increase the length of theyarn contact heaters to the point that it becomes awkward to operatethis equipment. From a practical viewpoint, of course, yarn heatercapacity cannot be increased indefinitely by simply increasing thelength of linear contact heaters. Furthermore, insulating andcontrolling very long contact heaters is far less efiicient than in thecase of more compact heating devices.

Moreover, when the thermal treatment to which the yarn is to besubjected is one wherein the yarn is to be heated in a highly twistedcondition, as in the case when false-twist bulking or texturingthermoplastic yarn, it is important that the attenuation of twist in theyarn during heating be held to a minimum. The problem of twistattenuation is more pronounced in machines which employ contact heaters.

If the twist is materially attenuated in the yarn along the length ofthe yarn heater so that there is a considerable twist gradient in theyarn being heated, the bulking, texturing or crimping imparted to theyarn will be of an uneven nature and therefore of a poor quality.

It is an object of this invention to provide a yarn heater which is morecompact for a given length of heating surface than those knownheretofore.

Another object of this invention is to provide a yarn heater whichcontinuously heats a section of yarn considerably longer than the lengthof the heater.

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Still another object of this invention is to provide improved means forbulking or texturing thermoplastic yarns continuously at very highlinear speeds.

Yet another object of this invention is to provide a yarn heater for thecontinuous heating of yarn being subjected to twisting, which heaterwill hold to a minimum the degree of attenuation in twist occurringduring heating.

Again another object of this invention is to provide an improved methodof heating yarns being subjected to twistmg.

The manner in which these and other objects and advantages of theinstant invention are realized will be apparent to those skilled in thisart from a consideration of this application, especially when taken inconjunction with the accompanying drawing.

SUMMARY OF THE INVENTION According to the instant invention, a yarnheater is provided which has a plurality of yarn heating surfaces andtwist propagating means disposed in the yarn path between thosesurfaces. The yarn, as it passes continuously along this yarn path, issubjected to thermal treatment and twisting so that the twistattenuation along the yarn path is minimal. This yarn heater may be anannular body, generally tubular in shape, having heating surfaces on theoutside as well as the inside of the tube and annular twist propagatingelements at the top and bottom of the tube. The twist propagatingelements may be friction twisters which are rotated as the yarn isadvanced along its yarn path, i.e. along the outside of the tube, overthe rotating twist-propagating member and then through the inside of thetube, over another rotating twist-propagating member and then again overthe outside of the tube, etc., in a number of passes. If desired, anumber of axial grooves may be placed on the outside of the tube so thatthe yarn travels through a different groove in each pass over theoutside of the yarn heater.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a schematic elevation of anembodiment of the apparatus of the instant invention;

FIGURE 2 is a somewhat schematic cross-sectional representation of thesame embodiment of the invention as seen on plane 22 indicated on FIGURE3;

FIGURE 3 is a plan view of the heater of the same embodiment of theinvention as is shown in FIGURE 1;

FIGURE 4 is a cross-sectional view as seen on plane 44 shown on FIGURE2;

FIGURE 5 is a schematic cross-sectional representation, analogous toFIGURE 4, of a somewhat modified embodiment of the heater of the instantinvention; and

FIGURE 6 is a schematic cross-sectional representation, analogous toFIGURE 4, of another somewhat modified embodiment of the heater of theinstant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The embodimentof the heater of this invention depicted in the drawing is shown incombination with elements employed in a false twisting apparatus. Itwill be understood, however, that the heater of the instant invention isuseful in other applications in which yarns are to be heated in acontinuous fashion.

The term yarn will be understood to embrace all textile strandlikematerials, including staple and multifilament yarns and filaments.Thermoplastic yarns include not only those formed from trulythermoplastic polymers such as nylons, polyesters, polyolefins andmixtures thereof with each other or with non-thermoplastic yarns, butalso yarns rendered functionally thermoplastic as by treatment withvarious solutions.

As may best be seen in FIGURE 1, the overall combination wherebythermoplastic yarn is false-twisted may comprise a creel 11 whereon ismounted yarn supply package 12, pretension control device 13, guide eye14 which may be mounted on an oscillatable bar, first tension controlassembly 15, heater assembly 16, primary false-twisting spindle 17 whichincludes twist-trapper 18, final tension assembly 19 with associatedoscillatably mounted guide eye 20 and take-up assembly 21.

First tension control assembly 15 com-prises a drive roll 31, idlerrolls 32 and 33 and tape 34. Similarly, final tension control assembly19 comprises drive roll 35, idler rolls 36 and 37 and tape 38. Yarntake-up assembly 21 comprises drive roll 41, yarn traversing means 42and take-up package 43.

The twist-trapper is a small cylindrical member of wear resistingmaterial transversely mounted over the central axis of a false twistspindle and adjacent to one extremity thereof, about which the yarn iswrapped one or more times for frictional engagement. All of theseelements are conventional components of a present day false-twistingmachine.

The yarn heater 16, as may best be seen in FIGURE 2, comprises anannular, generally tubular, heater body 51, the annulus of which definesa central opening or aperture 52 in which is concentrically androtatably mounted a tube 53 which rides on a plurality of bearings 54,55, 55a, and 56. These bearings are of the type capable of operating atelevated temperatures or extended periods without lubrication. Means forrotating this tube 53 about the axis of the opening 52 in the annularheater body 51 are provided in the form of pulley 57 and driving means58 associated therewith. Driving means 58 may conveniently comprise abelt such as a glass fiber impregnated V-belt, a compact tension springor a perforated steel band driven by a remote prime mover, or it maycomprise a prime mover located right within the heater, such as an airmotor or an electric motor adapted to operate at a temperature of ca.600 F.

Heating elements 59 whereby heater body 51 is heated may be electricalresistance heaters. Also provided, although not shown, are means tocontrol the energy imput to said heating means in order to achieve thedesired temperature conditions in the yarn being treated. As is wellknown in practice, the principal function of such controls is to permitselecting different levels of heater temperatures and to offset theeffect of changes in ambient temperature on the selected operatingtemperature.

Twist propagating elements 60 and 61Which in this embodiment are a pairof friction twistersare fixedly mounted, one adjacent to each of therespective extremities of tube 53, for rotation therewith. The twistpropagating elements are positioned adjacent to the respectiveextremities of the yarn heater body 51 and encircle the respectiveentrances to the opening 52 formed by the annular heating body and therespective extremities of tube 53. These twist propagating elements maybe formed of any convenient heat resistant material such as stainlesssteel, which may or may not have its yarn-contacting surfaces coatedwith Teflon. The twist-propagating elements employed in the embodimentshown in the drawing hereof are annular in nature and are, in fact,hemi-toroidal in shape. A hemi-toroidal shape is one which approximatesthat of a torus bisected by a plane containing the center of the torusand which is oriented so that the trace of the torus thereon is twoconcentric circles. It will be understood that the term embraces thoseshapes which are slightly distorted from that of a portion of a truetorus, as for instance the shape of elements 60 and 61 in FIGURE 2. Thusalthough surface 63 is cylindrical and surface 65 is conical thecombined surface 63, 64, 65 of twist-propagating element 60 performs inthis apparatus essentially as if it were hemi-toroidal and Will be soconsidered for the purpose of this invention. What is important is thatthe shape of these elements provides a smooth transition for the yarnpath from its axial procession through the inside of tube 53 to itsaxial procession in the opposite direction along the outside of heaterbody 51.

As may be seen in FIGURE 3, a plurality of axial grooves 66, 67, 68 and69, each running substantially the length of heater body 51, may bedistributed at any convenient spacing about the outside of heater body51. The entire heater body assembly may conveniently be insulated withthermal insulation contained within a housing indicated schematically at70.

In one preferred embodiment of the invention the dimensions oftwist-propagating elements 60 and 61 are such that the internal diameterthereof is slightly smaller than the diameter of the annular opening inthe heater, i.e. than the inner diameter of tube- 53. Likewise, theouter diameter of twist-propagating elements 60 and 61 is such that theyslightly overhang the external heat transfer surfaces, i.e. the bottomsof grooves 66, 67, 68 and 69. As a result, the yarn passing in multipleloops around twist-propagating elements 60 and 61 under tension aremaintained at a slight distance, such as 0.007 inch, from the heattransfer surfaces which they traverse. This results in minimizing thefrictional drag to which the yarn is subjected while being heatedaccording to the instant invention.

It will be understood that other heater configurations having aplurality of heating surfaces disposed in compact fashion on a heaterbody may be employed in this invention. Annular heaters are particularlysuited for this purpose because heating surfaces may be disposed in theopening formed by the annulus as well as on the exterior thereof. Thispermits the establishment of a yarn path which makes several passesthrough the opening and over the outside of the heater body, the yarn isbeing heated in each pass. FIGURES 5 and 6 illustrate somecross-sectional configurations of annular heaters which may be used.Thus the heater in FIGURE 5 has a square cross-section and that inFIGURE 6 has an oval crosssection.

Where twisted yarn is being heated, twist-propagating means are disposedin the yarn path in its transition between heating surfaces so that thetwist will not be greatly attenuated by the high friction contact whichthe yarn makes with the heater body as it changes direction. Where thesetwist-propagating means are friction twisters, their rate of rotation iscoordinated with the twisting speed of the primary twisting spindle tomaintain the twist attenuation in the yarn at an acceptably low level.

In operation, yarn is drawn from supply package 12 through pre-tensiondevice 13 and guide eye 14 to initial tensioning assembly 15. The slightoscillation imparted to guide eye 14 by the oscillating mounting assuresthat the yarn will not always follow exactly the same path throughinitial tensioning means 15 and thereby will avoid grooving drivenroller 31 thereof. The tension with which tape 34 is held against drivenroller 31 by idler rollers 32 and 33 assures that the yarn passesthrough initial control means 15 with substantially no slippage, so thatits rate of advance is controlled by the speed of rotation of drivenroller 31.

The yarn, now at a controlled, uniform tension, is then passed upwardlyover the outer surface of heater 51, as for instance through axialgroove 66 thereof, then over yarn twist propagating element 60 anddownwardly through the central opening in tube 53, around twistpropagating element 61 and again upwardly along the outside of heaterbody 51, this time through groove 67. In this fashion the yarn continuesto make successive passes over different heating surfaces of heater body51, alternately passing through the opening 52 formed by its annularshape and its outside heating surfaces in grooves 66, 67, 68 and 69.Each time the yarn passes from one heating surface to another it passesover one of the twist-propagating elements. In thus passing a pluralityof complete loops of yarn around the heater, the process of thisinvention subjects a length of yarn considerably longer than the lengthof the heater to thermal treatment.

Pulley 57 is driven by driving means 58 at a rate which may be relatedto the speed of primary twisting spindle 17 and the rate of yarnadvance, thereby rotating tube 53 and twist propagating elements 60 and61 attached thereto.

The yarn passes upwardly from the heater through primary twistingspindle 17 and around its twist trapper 18. After passing through finaltension controlling means 19 the yarn is wound up by take-up assembly21.

The additional tension applied to the traveling yarn by the multiplepasses around the heater surfaces contribute to an increase of yarntension in the heated Zone. For this reason it is preferable to selectfrom available twist trapper the types which add the least tension toyarns passing around them.

EXAMPLE A stretch yarn having permanent crimp is made from a continuousmultifilarnent 70 denier nylon on the apparatus depicted in the drawing.Yarn tension is maintained by tension control elements and 19 at 5grams, as measured below heater assembly 16, for this 70 denier yarn.Heater temperature is effectively maintained at 450 F. Tube 53 (andthereby twist propagating elements 60 and 61) are rotated at 1000 rpm.The primary twisting spindle 17 is rotated at 400,000 r.p.m. The yarn isadvanced through the apparatus at a rate of 415 feet per minute whichimparts a twist of 80 turns per inch thereto.

We claim:

1. Means for the continuous heating of twisted yarn comprising aplurality of yarn heating surfaces,

yarn twist-propagating means disposed between pairs of said surfaceswhereby a yarn path passing alternately over said yarn heating surfacesand said yarn twist-propagating means is defined,

energy supply means to provide heat at said surfaces,

and

yarn advancing means to move said yarn along said yarn path at thedesired rate.

2. The means of claim 1 wherein a plurality of said yarn heatingsurfaces are generally parallelly aligned surfaces of a single heaterbody.

3. The means of claim 2 wherein said heater body has an annularconfiguration and said heating surfaces are disposed in the openingformed by the annulus thereof as well as on the exterior thereof,whereby said yarn path passes alternately through said opening and overthe exterior of said heater body.

4. The means of claim 3 wherein said yarn twist-prop agating means aredisposed adjacent to the opening formed by said annulus.

5. The means of claim 3 wherein said heater body is generally tubular inshape.

6. The means of claim 3 wherein said heater body is generally square incross-section.

7. The means of claim 3 wherein said heater body is generally oval incross-section.

8. The means of claim 4 wherein said yarn twist-propagating means areannular in shape and rotatably mounted.

9. The means of claim 4 wherein said yarn twist-propagating means areannular bodies having an internal diameter slightly smaller that that ofthe annular aperture of said heater body and an external diametersufiicient to slightly overhang the exterior heating surfaces of saidtubular body.

10. The means of claim 4 further comprising means to separate thevarious passes of said yarn path over the exterior of said heater bodyfrom one another.

11. The means of claim 9 wherein said yarn twist-propagating means areeach mounted for rotation in planes generally perpendicular to the axisof said heater body and wherein the yarn-contacting surfaces of saidtwistpropagating means are adapted, when rotated, to twist said yarn.

12. The means of claim 11 wherein the exterior of said heater bodycontains a plurality of axial grooves whereby said yarn path passesalternately through said annulus, over one of said yarntwist-propagating means, through one of said axial grooves, over theother of said yarn twist-propagating means and back through said annulusto repeat the cycle, passing through another of said grooves in eachcycle.

13. A heater for continuously heating yarn passing therethroughcomprising a plurality of highly heat-conductive heat trasfer surfacesdisposed in the annular opening and on the exterior of an elongatedannular heater body, means to heat said heat transfer surfaces and meansto advance said yarn past said heat transfer surfaces.

14. The heater of claim 13 further comprising a number of axial grooveson the exterior of said heater, said number being less than the numberof said highly heatconductive heat transfer surfaces, one of said highlyheat conductive heat transfer surfaces being disposed in each of saidgrooves.

15. The heater of claim 13 further comprising means to move the saidhighly heat conductive heat transfer surface disposed in the annularopening thereof about the axis of said opening while said yarn is beingadvanced therethrough.

16. Yarn heating means comprising an elongated annular heater body,

a tube mounted for rotation about its axis in the opening formed by theannulus of said heater body,

a pair of annular yarn twist-propagating means fixedly attached to therespective extremities of said tube for rotation therewith,

means to rotate said tube in said heater body,

means to heat said heater body, and

a highly heat conductive surface on the exterior of said heater body.

17. The yarn heating means of claim 16 further comprising a plurality ofaxial grooves on the exterior of said heater body and a highly heatconductive surface disposed in each of said grooves.

18. A yarn heater for the continuous heating of twisted yarn comprisingan elongated annular highly heat-conductive body,

a pair of hemi-toroidal members,

one of said members being rotatably mounted adjacent to each of therespective extremities of said body so as to encircle the entrance tothe opening formed by the annulus thereof, and means to heat said body.

19. The yarn heater of claim 18 wherein said hemitoroidal members eachhave an inside diameter slightly smaller than that of said opening and abody thickness slightly greater than that of said body.

20. The yarn heater of claim 18 further comprising a tube concentricallyrotatably mounted in said opening,

means to rotate said tube about the axis of said opensaid hemi-toroidalmembers being mounted on the respective extremities of said tube forrotation therewith.

21. The yarn heater of claim 16 in combination with yarn twisting meansaligned to permit the twist imparted by said yarn twisting means to runbackward along the yarn passing through said yarn heater, a twisttrapper disposed on said yarn twisting means and on the opposite sidethereof from said yarn heater, and yarn advancing means to move saidyarn through said combination.

22. The combination of claim 21 further comprising means to rotate saidtwist-propagating means at a rate correlated with that of said twistingmeans.

23. The combination of claim 21 further comprising yarn let-off means,yarn take-up means and yarn tension control means, whereby means areprovided to let off yarn from a package, to pass said yarn continuouslythrough said heater and said twisting means under controlled tension,and twist running backward through said heater with minimum attenuationand being trapped in the opposite direction, and to rewind said yarn ona package.

24. The combination of claim 23 further comprising means to correlatethe rate of operation of said yarn tension control means, said yarntwisting means and said twist-propagating means.

25. The method of continuously heating a yarn while said yarn is beingsubjected to twisting comprising running a plurality of passes of saidyarn around a heater and twisting said yarn between said passes topropagate the twist to all of said passes.

26. The method of claim 25 wherein said yarn makes a plurality of turnsthrough the opening in an annular heater and around the outside thereofand is twisted each time it passes from the outside of said heater intosaid opening and from said opening to said outside.

27. In the process of continuously crimping thermoplastic yarn bypassing said yarn under tension sequentially through a heating zone, acooling zone and false twisting means whereby there is imparted to saidyarn a false twist which runs backward through said yarn into saidcooling zone and said heating zone, the improvement comprising passingsaid yarn in at least one loop through the annular opening and adjacentthe exterior of an annular heating means in said heating zone.

28. The improvement of claim 27 wherein said yarn is subjected toadditional twisting in said heating zone.

29. In the process of continuously crimping thermoplastic yarn bypassing said yarn under tension sequentially through a heating zone, acooling zone and false twisting means whereby there is imparted to saidyarn a false twist which runs backward through said yarn into saidcooling zone and said heating zone, the improvement comprising passingsaid yarn in a plurality of complete loops about heating means in saidheating zone wherein each said loop of said yarn is subjected toadditional twisting in said heating zone.

30. The improvement of claim 27 wherein said yarn in said heating zoneis substantially longer than said heating zone.

31. In the process of continuously crimping thermoplastic yarn bypassing said yarn under tension sequentially through a heating zone, acooling zone and false twisting means whereby there is imparted to saidyarn a false twist which runs backward through said yarn into saidcooling zone and said heating zone, the improvement comprisingadditionally imparting twist within said heating zone to said yarn.

32. In the process of continuously crimping thermoplastic yarn bypassing said yarn under tension sequentially through a heating zone, acooling zone and false twisting means whereby there is imparted to saidyarn a false twist which runs backward through said yarn into saidcooling zone and said heating zone, the improvement comprisingadditionally twisting said yarn in said heating zone wherein the saidadditional twisting in said heating zone is of a magnitude to minimizethe twist gradient in said yarn.

33. A heater for continuously heating yarn passing therethroughcomprising a highly heat conductive heat transfer surface on both theannular interior and the exterior of an elongated annular heater body,at least one of said surfaces on said annular interior and said exteriorbeing characterized by a plurality of heat transfer surface locations,means to heat said heat transfer surfaces and means to advance said yarnpast said heat transfer surfaces.

34. The heater of claim 33 further comprising a plurality of axialgrooves on the exterior of said heater, one of said heat transfersurface locations being disposed in juxtaposition to each of saidgrooves.

35. The heater of claim 33 further comprising means to move the saidhighly heat conductive heat transfer surface disposed in the annularinterior thereof about the axis of said interior while said yarn isbeing advanced therethrough.

36. In the process of continuously crimping thermoplastic yarn bypassing said yarn under tension sequentially through a heating zone, acooling zone and false twisting means whereby there is imparted to saidyarn a false twist which runs backward through said yarn into saidcooling zone and said heating zone, the improvement comprising loopingsaid yarn about heating means in said heating zone such that said yarnis heated by adjacent but separate heating surfaces on said heatingmeans.

37. The improvement of claim 36 wherein said yarn is subjected toadditional twisting in said heating zone.

38. The improvement of claim 37 wherein the said additional twisting insaid heating zone is of a magnitude to minimize the twist gradient insaid yarn.

39. The improvement of claim 27 additionally comprising minimizing thetwist attenuation of said yarn within said heating zone.

40. The improvement of claim 27 additionally comprising minimizing thetwist attenuation of said yarn within said heating zone by passing saidyarn in contact with twist propagating means.

41. The process of continuously crimping thermoplastic yarn by passingsaid yarn under tension sequentially through a heating zone, a coolingzone and false twisting means whereby there is imparted to said yarn afalse twist which runs backward through said yarn into said cooling zoneand said heating zone, the improvement comprising minimizing the twistattenuation of said yarn within said heating zone by passing said yarnin contact with the surface of twist propagating means which move in adirection transverse to the longitudinal axis of said yarn.

42. The improvement of claim 36 additionally comprising minimizing thetwist attenuation of said yarn within said heating zone.

43. The improvement of claim 42 wherein said minimizing of the twistattenuation is performed by passing said yarn in contact with twistpropagating means located References Cited UNITED STATES PATENTS2,203,561 6/1940 Broder 2862 2,477,909 8/1949 Stockly 57-l57 XR2,951,330 9/1960 Bouvet 57l57 XR 2,959,906 11/1960 Richter 5734 FOREIGNPATENTS 901,922 7/1962 Great Britain.

STANLEY N. GILREATH, Primary Examiner WERNER H. SCHROEDER, AssistantExaminer US. Cl. X.R. 2862; 57-157 21% UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,469,384 Datedje t ber 30 1969Inventor(s) N. J. Stoddard, et al It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Claim 13, line 3; change "trasfer" to-transfer.

Claim 43, line 3; after "located" insert-at the separation of saidadjacent heating surfaces.-.

SIGNED AND SEALED JAN 2 0-1970 SEAL) Attest:

WILLIAM E. 50mm.

Attesting Officer

